diff --git a/audioread/ffdec.py b/audioread/ffdec.py
index d957034..ad4f448 100644
--- a/audioread/ffdec.py
+++ b/audioread/ffdec.py
@@ -202,7 +202,7 @@ def read_data(self, timeout=10.0):
                         # Nothing interesting has happened for a while --
                         # FFmpeg is probably hanging.
                         raise ReadTimeoutError('ffmpeg output: {}'.format(
-                            ''.join(self.stderr_reader.queue.queue)
+                            b''.join(self.stderr_reader.queue.queue)
                         ))
                     else:
                         start_time = end_time